feat(chat): handle credit-gated send responses

src/data/dto/chat/chat_send_response.ts

@@ -17,6 +17,12 @@ export class ChatSendResponse {
   declare readonly timestamp: number;
   declare readonly image: ChatImageData;
   declare readonly lockDetail: ChatLockDetailData;
+  declare readonly canSendMessage: boolean;
+  declare readonly cannotSendReason: string | null;
+  declare readonly creditBalance: number;
+  declare readonly creditsCharged: number;
+  declare readonly requiredCredits: number;
+  declare readonly shortfallCredits: number;
 
   private constructor(input: ChatSendResponseInput) {
     const data = ChatSendResponseSchema.parse(input);

src/data/schemas/chat/chat_send_response.ts

@@ -3,17 +3,24 @@
  * 
  */
 import { z } from "zod";
+import { booleanOrFalse, stringOrNull } from "../nullable-defaults";
 import { ChatImageSchema, ChatLockDetailSchema } from "./chat_payloads";
 
 export const ChatSendResponseSchema = z.object({
   reply: z.string(),
   audioUrl: z.string().default(""),
   messageId: z.string(),
-  isGuest: z.boolean().default(false),
+  isGuest: booleanOrFalse,
   // 函数式 default —— 每次 parse 时重新调 Date.now()（后端不返回 timestamp 时用当下时间）
   timestamp: z.number().default(() => Date.now()),
   image: ChatImageSchema,
   lockDetail: ChatLockDetailSchema,
+  canSendMessage: z.boolean().default(true),
+  cannotSendReason: stringOrNull,
+  creditBalance: z.number().default(0),
+  creditsCharged: z.number().default(0),
+  requiredCredits: z.number().default(0),
+  shortfallCredits: z.number().default(0),
 });
 
 export type ChatSendResponseInput = z.input<typeof ChatSendResponseSchema>;

src/data/schemas/nullable-defaults.ts

@@ -18,6 +18,9 @@ export const stringOrEmpty = z
   .transform((v) => v ?? "")
   .default("");
 
+/** `string | null | undefined` → `string | null`（默认 null） */
+export const stringOrNull = z.string().nullable().default(null);
+
 /** `number | null | undefined` → `number`（默认 0） */
 export const numberOrZero = z
   .number()
@@ -30,4 +33,4 @@ export const booleanOrFalse = z
   .boolean()
   .nullable()
   .transform((v) => v ?? false)
-  .default(false);
+  .default(false);